1. Field of the Invention
This invention relates to instruments and methods for orthopedic surgery generally and more specifically to elastic cables adapted for fixation of fractured bones.
2. Description of the Related Art
In various medical procedures wires or cables are used to join or stabilize fractured bones. Typically, metal alloy cables are preferred; but synthetic polymer cables are sometimes employed. For example, U.S. Pat. No. 6,093,190 to Mattchen describes a method of using elastomeric cables to stabilize and compress fractured bones, by spanning a network of tensioned cables across a fracture. Such a network can provide stable fixation of a fracture in both linear and torsional directions. The method disclosed also provides a tensile preload across the fracture, tending to compress the fracture and maintain fixation despite tensile and shear loads (such as those resulting from movement, weight bearing and bone remodeling).
In addition to the use of cables in more-or-less permanent surgical implants, surgeons commonly find use for temporary tensile connections during orthopedic surgery. Often surgical techniques demand temporary application of tension to counteract muscles and ligaments or otherwise to manipulate bony structures.
In most cases, wires or cables are manipulated during surgery without the benefit of an accurate measurement of the applied tension. From time to time, however, it is desirable to tense an orthopedic cable to a specific, predetermined amount of force. Instruments are known, such as strain gauges and scales, that are capable of accurately measuring cable tension; Instruments have been devised to tension a cable to a predetermined force. However, such devices are often inconvenient, unwieldy, and expensive. Such instruments require routine calibration and maintenance. In addition, such instruments must be designed to withstand sterilization conditions (including autoclave temperatures). Some orthopedic devices have been introduced that attempt to provide a visual indication of tension. See, for example, U.S. Pat. No. 4,936,843 to Sohngen (1990). Nevertheless, a need persists for a simple, convenient means of measuring and displaying cable tension in the context of orthopedic surgery.